Organotin stabilizer composition containing more than 20 percent tin and resin compositions containing the same

ABSTRACT

A polyvinyl chloride resin stabilizer is provided having a high concentration of tin, in the range from about 20 to about 35% by weight, and a high concentration of sulfur, within the range from about 10 to about 25% sulfur, comprising .[.an.]. .Iadd.a di .Iaddend.organotin .Iadd.di .Iaddend.alpha- or beta-mercapto carboxylic acid ester and an organotin sulfide. 
     Polyvinyl chloride resin compositions are also provided containing these stabilizers.

This invention relates to a stabilizer composition for polyvinylchloride resins and to polyvinyl chloride resin compositions havingimproved resistance to deterioration at 350° F. and more particularly,to a stabilizer composition comprising an organotin mercapto carboxylicacid ester and an organotin sulfide having a high concentration of tin,and to polyvinyl chloride resin compositions containing suchstabilizers.

The stabilizing effectiveness of organotin stabilizers for polyvinylchloride resins is generally associated with organotin groups, tincontent, and, to some degree, sulfur content. The higher the relativeproportion of these, the more effective the organotin compound usuallyis as a stabilizer. However, there are exceptions to the rule that makeprediction fallible.

The organotin sulfides, for example, offer the highest tin and sulfurcontents per organotin group, and yet they are not the best stabilizers,and have never found a place as a commercial stabilizer. Despite theirconsiderably lower tin and sulfur contents, the most effective organotinstabilizers presently in use, and the recognized standard for judgingother organotin stabilizers, are the organotin mercapto carboxylic acidesters. The great majority of these materials, and certainly all of themost commonly used commercial products, are either liquid at roomtemperatures or are low-melting solids. The addition of even a smallproportion of a liquid stabilizing additive has unfavorable effects onthe heat distortion temperature and the impact strength of polyvinylchloride resins. As a result, it is difficult to provide a high degreeof chemical stability and a high degree of structural stability,problems which generally go hand in hand when rigid resins are subjectedto high temperature conditions. To attain both of these goals, it isnecessary to use as small an amount of the stabilizer as possible, sothat the structural strength of the resin is least affected.

The use of the organotin mercapto carboxylic acid esters as stabilizersfor polyvinyl chloride resins is well known, and is generally set forthin such early patents as U.S. Pat. Nos. 2,753,325 to Leistner et al.,issued June 26, 1956, 2,641,596 to Leistner et al., issued June 9, 1953,and 2,648,650 to Weinberg et al., issued Aug. 11, 1953.

The organotin sulfides are described in U.S. Pat. No. 2,746,946 toWeinberg et al., dated May 22, 1956. Polymeric organotin sulfides havinga high proportion of tin and sulfur by weight have also been suggested.Examples of such materials are given in U.S. Pat. No. 3,021,302 to Frey,dated Feb. 13, 1962, which discloses polymeric condensation products ofhydrocarbon stannonic acid, hydrocarbon thiostannonic acid andco-condensation products of these materials. However, all of thesematerials have suffered from one or another failing, which until now hasprevented their coming into general commercial use.

Similar disclosures of polymeric organotin compounds, which generallyinclude a chain of tin atoms connected through oxygen or sulfur atoms,are set out in U.S. Pat. Nos. 2,597,920, dated Apr. 15, 1962; 2,626,953,dated Jan. 27, 1953; 2,628,211, dated Feb. 10, 1953; 2,746,946, datedMay 22, 1956; 3,184,430, dated May 18, 1956; and 2,938,103, dated May24, 1960.

U.S. Pat. No. 2,809,956, dated Oct. 15, 1957, discloses polymericorganotin compounds which include mercapto ester groups attached to tin,having the general formula: ##STR1## wherein SX can be a mercapto;mercapto alcohol or ester; or mercapto acid ester group. Thesecompounds, however, have been found not to be as effective stabilizersas the monomeric organotin mercapto acid esters, such as dibutyltinbis(isooctyl thioglycolate).

U.S. Pat. Nos. 3,078,390, 3,196,129 and 3,217,004 describe a series ofthioacetal and thioketal organotin carboxylate salt stabilizers whichcan be prepared in situ by the reaction of thioacetal and thioketalcarboxylic acids with dihydrocarbontin oxides or sulfides or thecorresponding monohydrocarbon- or trihydrocarbontin compounds.

According to the present invention, a particularly effective polyvinylchloride resin stabilizer composition is provided having a relativelyhigh concentration of tin, within the range from about 20 to about 35%Sn, and a relatively high concentration of sulfur, within the range fromabout 10 to about 25% S, and comprising (a) .[.an organotin.]. .Iadd.adiorganotin di .Iaddend.α- or β-mercapto carboxylic acid ester, and (b)an organotin sulfide.

The organotin sulfides useful in this combination each contain groupslinked to tin only through carbon, and a sulfide sulfur group, ═S,wherein the sulfide sulfur valences are linked to the same tin atom orto different tin atoms. Each compound contains per tin atom one or twohydrocarbon or heterocyclic groups linked to tin through carbon. Forbest results, and to obtain a synergistic stabilizing effectiveness, atleast one of the compounds of the combination of this invention shouldcontain only one hydrocarbon group per tin atom, linked to tin through acarbon atom. This combination generally improves the initial color of aresin composition during heating, i.e., during the first thirty minutesof a heat test, and can also improve the long-term stability beforefinal charring.

One type of the organotin sulfides useful in this invention can bedefined by the formula:

    R.sub.2 SnS

wherein R is a hydrocarbon group linked to tin through carbon, andcontaining from one to about eight carbon atoms. The atomic ratio ofsulfur to tin is 1:1.

Another group of organotin sulfides of this invention are polymers whichcan be illustrated by the formulae ##STR2## in which each tin atom islinked to three sulfur atoms and each sulfur is linked to two tin atoms,and x is a number from one to about 100.

Another type has the recurring group ##STR3## where n is the number ofunits in the chain, and ranges up to 100 and more.

Another way of defining the R₂ SnS type is: ##STR4##

The R's are as defined above. The above formulae are not intended tolimit the structure of the compound in any way. The structures can bestraight chain, branched chain, cyclic, or any combination thereof.

The R hydrocarbon groups in the above formulae can be selected fromamong alkyl, aryl, cycloalkyl, alkyl cycloalkyl, cycloalkylalkyl, andarylalkyl having from one to eight carbon atoms.

The preferred R groups are alkyl groups having from four to eight carbonatoms.

The organotin sulfides used in this invention are well known to the artand can be prepared by a number of procedures described in earlierreferences which are known to the art. For example, hydrogen sulfide canbe bubbled, at about 40° C. into a slurry of hydrocarbontin oxide inwater or an organic solvent (such as methanol, acetone, or toluene). Theinsoluble oxide is converted to a solution or dispersion of the sulfideand the reaction is terminated when the entire system is liquefied.

Another useful technique is the displacement of hydrocarbontin halide(e.g. Bu₂ SCl₂) by an aqueous alkali metal sulfide or ammonium sulfide.Hydrocarbontin sulfides also can be prepared from the interaction ofhydrocarbontin halide with other sulfur compounds than sulfides, such assodium thiosulfite and ammonium polysulfide. These reactions provideunstable intermediates that decompose to the hydrocarbontin sulfide plusanother product characteristic of the particular starting materials,e.g. alkali metal sulfide or free sulfur.

All the above preparative methods can be summarized in thetransformations below, where the n-butyltin compounds shown arerepresentative of the entire class of organotin compounds: ##EQU1##

When these preparations are carried out in an aqueous medium, a smallproportion of the sulfur atoms in the hydrocarbontin sulfides arereplaced by oxygen atoms, resulting in sulfur-deficient products havingaverage compositions represented by the empirical formulae

    (R.sub.2 SnS.sub.p O.sub.1-p)

and ((RSn)₂ S_(r) O_(2-r))_(x), where p is at least 0.85 and r is atleast 1.5.

In the stabilizer composition of this invention these sulfides are fullyas effective as the pure oxygen-free sulfides, and wherever organotinsulfides are mentioned the term is intended to include both the purecompounds and the sulfur-deficient preparations.

There are many other procedures for the preparation of these compounds.The above list of procedures is not intended to be exhaustive. Organotinsulfides prepared by any other procedure would also be useful in thepresent combination.

The R groups linked to tin through carbon can, for example, be methyl,ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl,amyl, hexyl, octyl, 2-ethylhexyl, isooctyl, phenyl, benzyl, cumyl,tolyl, xylyl, cyclohexyl, and cyclopentyl.

Preferred examples of organotin sulfides are dipropyltin sulfide,dibutyltin sulfide, butyltin sesquisulfide

    ((BuSn).sub.2 S.sub.3).sub.x

(x═from 1 to 100 or higher), di-n-pentyltin sulfide, hexyltinsesquisulfide, dihexyltin sulfide, isooctyltin sesquisulfide,di-2-ethylhexyltin sulfide, heptyltin sesquisulfide, di(isobutyl)tinsulfide, n-octyltin sesquisulfide, di-(n-octyltin) sulfide andsec-butyltin sesquisulfide propyltin sesquisulfide, dimethyltin sulfide,isoamyltin sesquisulfide, di(isoamyl)tin sulfide, diisohexyltin sulfide,2-ethylhexyltin sesquisulfide, 2-ethyl butyltin sulfide.

The above compounds can have any degree of polymerization falling withinthe above formula.

The .[.organotin mercapto.]. .Iadd.diorganotin dimercapto .Iaddend.acidesters can be monomeric or polymeric, but preferably monomeric. Themonomers can be defined as organotin compounds having organic radicalslinked to tin only through carbon and sulfur, and have the generalformula:

    .[.R'.sub.n Sn--[S--Z.sub.1 --(COOR").sub.m ].sub.4-n .].

    .Iadd.R'.sub.2 Sn--[S--Z.sub.1 --COOR").sub.m ].sub.2 .Iaddend.( 1)

The S--Z₁ --COOR" group is derived from an α- or β-mercapto carboxylicacid ester.

.[.n is an integer from one to two..].

m is the number of COOR" groups and is an integer from one to four.

R" is an organic group derived from a monohydric or polyhydric alcoholhaving from one to about four hydroxyl groups and from about one toabout fifteen carbon atoms. If there is more than one COOR" group, theR" radicals can be the same or different.

R' is a hydrocarbon radical having from about one to about eight carbonatoms, preferably from four to eight, and includes the groups definedabove for R.

Z₁ is a bivalent alkylene radical carrying the S and COOR" groups, andin addition can contain free carboxylic acid groups, carboxylic acidsalt groups and mercapto groups. The Z₁ radical has from one to aboutfive carbon atoms.

The S--Z₁ --(COOR")_(m) groups are derived from mono- or poly α- andβ-mercapto carboxylic acid esters by removal of the hydrogen atom of themercapto group. These include the esters of aliphatic acids whichcontain at least one mercapto group, such as, for example, esters ofmercaptoacetic acid, α- and β-mercaptopropionic acid, α- andβ-mercaptobutyric acid and α- and β-mercaptovaleric acid, thiomalicacid, α- and β-mercaptoglutaric acid, mercaptomalonic acid, α- andβ-mercaptoadipic acid and α- and β-mercaptopimelic acid.

R" is an organic group derived from a monohydric or polyhydric alcoholof the formula R(OH)_(n4), where n₄ is an integer from one to aboutfour, but is preferably one or two. Thus, R" can be alkyl, alkylene,alkenyl, aryl, arylene, mixed alkyl-aryl, mixed aryl-alkyl,cycloaliphatic and heterocyclic, and can contain from about one to aboutfifteen carbon atoms, and can also contain ester groups, alkoxy groups,hydroxyl groups, halogen atoms and other inert substituents. Preferably,R" is derived from a monohydric alcohol containing from one to aboutfifteen carbon atoms, such as methyl, ethyl, propyl, s-butyl, n-butyl,t-butyl, isobutyl, octyl, isoctyl, 2-ethylhexyl, 2-octyl, decyl, lauryl,cyclic monohydric alcohols, such as cyclopropanol,2,2-dimethyl-1-cyclopropanol, cyclobutanol, 2-phenyl-1-cyclobutanol,cyclopentanol, cyclopentenol, cyclohexanol, cyclohexenol, 2-methyl-,3-methyl-, and 4-methyl-cyclohexanol, 2-phenyl-cyclohexanol,3,3,5-trimethyl cyclohexanol, cycloheptanol, 2-methyl-, 3-methyl-and4-methyl cycloheptanol, cyclooctanol, cyclononanol, cyclodecanol,cyclododecanol, or from a dihydric alcohol such as glycols containingfrom two to about fifteen carbon atoms, including ethylene glycol,propylene glycol, diethylene glycol, dipropylene glycol, tetramethyleneglycol, neopentyl glycol and decamethylene glycol, 2,2,4-trimethylpentane-diol, 2,2,4,4-tetramethyl cyclobutanediol,cyclohexane-1,4-dimethanol, and polyols such as glycerine, triethylolpropane, mannitol, sorbitol, erythritol, dipentaerythritol,pentaerythritol, and trimethylol propane.

It is not necessary for the alcohol R(OH)_(n4) to be a single, purecompound. Many of the commercially available and inexpensive alcoholmixtures are suitable and advantageous. The branched-chain primaryalcohols made by the Oxo process and known as isooctyl, isodecyl andisotridecyl alcohols are mixtures of isomers, but can be used as if theywere single compounds. Other alcohol mixtures that can be used includemixed homologous primary alcohols arising from oxidation of the reactionproduct of ethylene with triethyl aluminum, isomers and homologoussecondary alcohols from the hydration of linear C₅ to C₁₅ olefins or theoxidation of linear C₆ to C₁₅ paraffins, isomers and homologousstraight-chain and methyl-branched primary alcohols resulting from theapplication to the Oxo process to C₆ to C₁₄ linear alpha-olefins,homologous mixtures of reaction products from ethylene oxide withalcohols, phenols or carboxylic acids of the proper carbon content andthe like.

These mercapto acid esters, where not known, can be readily prepared byreaction of the mercaptocarboxylic acid esters with the correspondingorganotin oxide or chloride. For a more complete explanation of theprocess for making, and for additional examples of these diorganotinmercapto ester compounds, see U.S. Pat. Nos. 2,648,650 to Weinberg etal., 2,641,596 and 2,752,325 to Leistner, and 3,115,509 to Mack, andCanadian Pat. No. 649,989 to Mack.

The organotin mercapto acid esters containing two different mercaptoacid ester groups can be prepared by reacting the desired organotinoxide or chloride with a mixture of the mercapto acid esters, or byheating the two different organotin esters together.

The following organotin thioesters are typical of those coming withinthe invention:

    __________________________________________________________________________      1.                                                                                ##STR5##                                                                  2.                                                                                ##STR6##                                                                  .[.3.                                                                             ##STR7##                                                                .Iadd.3..Iaddend.                                                               .[.4..].                                                                          ##STR8##                                                                .Iadd.4..Iaddend.                                                               .[.5..].                                                                          ##STR9##                                                                .Iadd.5..Iaddend.                                                               .[.6..].                                                                          ##STR10##                                                                 .[.7.                                                                             ##STR11##                                                               .Iadd.6..Iaddend.                                                               .[.8..].                                                                          ##STR12##                                                               .Iadd.7..Iaddend.                                                               .[.9..].                                                                          ##STR13##                                                               .Iadd.8..Iaddend.                                                               .[.10..].                                                                         ##STR14##                                                               .Iadd.9..Iaddend.                                                               .[.11..].                                                                         ##STR15##                                                               .Iadd.10..Iaddend.                                                              .[.12..].                                                                         ##STR16##                                                               .Iadd.11..Iaddend.                                                              .[.13..].                                                                         ##STR17##                                                               .Iadd.12..Iaddend.                                                              .[.14..].                                                                         ##STR18##                                                               .Iadd.13..Iaddend.                                                              .[.15..].                                                                         ##STR19##                                                               .Iadd.14..Iaddend.                                                              .[.16..].                                                                         ##STR20##                                                               .Iadd.15..Iaddend.                                                              .[.17..].                                                                        [CH.sub.3 ].sub.2 Sn[SCH.sub.2COOCH.sub.2 CH.sub.3 ].sub.3                 .[.18..].                                                                         ##STR21##                                                               .Iadd.17..Iaddend.                                                              .[.19..].                                                                         ##STR22##                                                               .Iadd.18..Iaddend.                                                              .[.20..].                                                                         ##STR23##                                                               .Iadd.19..Iaddend.                                                              .[.21..].                                                                         ##STR24##                                                               .Iadd.20..Iaddend.                                                              .[.22..].                                                                         ##STR25##                                                               .Iadd.21..Iaddend.                                                              .[.23..].                                                                         ##STR26##                                                                 .[.24.                                                                            ##STR27##                                                               __________________________________________________________________________

Specific combinations of organotin sulfides with organotin mercaptocarboxylic esters that can be used according to this invention includethe following:

di-n-butyltin sulfide+di-n-butyltin bis(isooctyl thioglycolate)

.[.di-n-octyltin sulfide+n-butyltin tris(cyclohexyl thioglycolate).].

n-butyltin sesquisulfide+di-n-butyltin bis(di-n-butyl thiomaleate)

n-butyltin sesquisulfide+di-n-octyltin bis(isooctyl thioglycolate)

n-octyltin sesquisulfide+di-n-propyltin bis(2-ethylhexylbeta-mercaptopropionate)

di-n-octyltin sulfide+di-n-octyltin bis(isooctyl thioglycolate)

n-octyltin sesquisulfide+di-n-octyltin bis(isooctyl thioglycolate)

.[.di-n-octyltin sulfide+n-octyltin tris(isooctyl thiolglycolate).].

.[.n-octyltin sesquisulfide+n-octyltin tris(isooctyl thioglycolate).].

n-butyltin sesquisulfide+di-n-butyltin bis(isooctyl thioglycolate)

dicyclohexyltin sulfide+di-n-butyltin bis(isooctyl thioglycolate)

cyclohexyltin sesquisulfide+di-n-octyltin bis(isooctyl thioglycolate)

n-propyltin sesquisulfide+dicyclohexyltin bis(cyclohexyl thioglycolate)

di-2-ethylhexyltin sulfide+di-n-butyltin bis(2-ethylbutyl thioglycolate)

.[.di-n-butyltin sulfide+n-butyltin tris(2-ethoxyethylalpha-mercaptopropionate).].

di-isobutyltin sulfide+di-isobutyltin bis(tetrahydrofurfurylbeta-mercaptopropionate)

t-butyltin sesquisulfide+di-2-ethylhexyltin bis(methyl thioglycolate)

.[.phenyltin sesquisulfide+phenyltin tris(phenoxyethyl thioglycolate).].

ethyltin sesquisulfide+di-n-butyltin bis(isooctyl thioglycolate)

.[.diphenyltin sulfide+ethyltin tris(2-ethylhexanoyloxyethylthioglycolate).].

isopropyltin sesquisulfide+di-n-butyltin bis(2,2-dimethylpentylthioglycolate)

isoamyltin sesquisulfide+di-n-propyltin bis(2-octylalphamercaptopropionate)

n-butyltin sesquisulfide+di-n-butyltin 4,4-isopropylidene di(cyclohexylthioglycolate)

.[.di-n-butyltin sulfide+n-butyltin glyceryl tri(thioglycolate).].

The invention is applicable to any polyvinyl chloride resin. The term"polyvinyl chloride" as used herein is inclusive of any polymer formedat least in part of the recurring group ##STR28## and having a chlorinecontent in excess of 40%. In this group, the X groups can each be eitherhydrogen or chlorine. In polyvinyl chloride homopolymers, each of the Xgroups is hydrogen. Thus, the term includes not only polyvinyl chloridehomopolymers but also after-chlorinated polyvinyl chlorides such asthose disclosed in British Pat. No. 893,288 and also copolymers of vinylchloride in a major proportion and other copolymerizable monomers in aminor proportion, such as copolymers of vinyl chloride and vinylacetate, copolymers of vinyl chloride with maleic or fumaric acids oresters, and copolymers of vinyl chloride with styrene, propylene, andethylene. The invention also is applicable to mixtures of polyvinylchloride in a major porportion with other synthetic resins such aschlorinated polyethylene or a copolymer of acrylonitrile, butadiene andstyrene. Among the polyvinyl chlorides which can be stabilized are theuniaxially-stretch oriented polyvinyl chlorides described in U.S. Pat.No. 2,984,593 to Isaksem et al., that is, syndiotactic polyvinylchloride, as well as atactic and isotactic polyvinyl chlorides.

The stabilizing combinations of this invention, both with and withoutsupplementary stabilizers, are excellent stabilizers for bothplasticized and unplasticized polyvinyl chloride resins. Whenplasticizers are to be employed, they may be incorporated into thepolyvinyl chloride resins in accordance with conventional means. Theconventional plasticizers can be used, such as dioctyl phthalate,dioctyl sebacate and tricresyl phosphate. Where a plasticizer isemployed, it can be used in an amount within the range from 0 to 100parts by weight of the resin.

Particularly useful plasticizers are the epoxy higher esters having fromabout twenty to about one hundred fifty carbon atoms. Such esters willinitially have had unsaturation in the alcohol or acid portion of themolecule, which is taken up by the formation of the epoxy group.

Typical unsaturated acids are oleic, linoleic, linolenic, erucic,ricinoleic and brassidic acids, and these may be esterified with organicmonohydric or polyhydric alcohols, the total number of carbon atoms ofthe acid and the alcohol being within the range stated. Typicalmonohydric alcohols include butyl alcohol, 2-ethylhexyl alcohol, laurylalcohol, isooctyl alcohol, stearyl alcohol, and oleyl alcohol. The octylalcohols are preferred. Typical polyhydric alcohols includepentaerythritol, glycerol, ethylene glycol, 1,2-propylene glycol,1,4-butylene glycol, neopentyl glycol, ricinoleyl alcohol, erythritol,mannitol and sorbitol. Glycerol is preferred. These alcohols may befully or partially esterified with the epoxidized acid. Also useful arethe epoxidized mixtures of higher fatty acid esters found innaturally-occurring oils such as epoxidized soybean oil, epoxidizedolive oil, epoxidized cottonseed oil, epoxidized tall oil fatty acidesters, epoxidized linseed oil and epoxidized tallow. Of these,epoxidized soybean oil is preferred.

The alcohol can contain the epoxy group and have a long or short chain,and the acid can have a short or long chain, such as epoxy stearylacetate, epoxy stearyl stearate, glycidyl stearate, and polymerizedglycidyl methacrylate.

A small amount, usually not more than 1.5%, of a parting agent orlubricant, also can be included. Typical parting agents are the higheraliphatic acids, and salts having twelve to twenty-four carbon atoms,such as stearic acid, lauric acid, palmitic acid and myristic acid,lithium stearate and calcium palmitate, mineral lubricating oils,polyvinyl stearate, polyethylene and paraffin wax.

Impact modifiers, for improving the toughness or impact-resistance ofunplasticized resins, can also be added to the resin compositionsstabilized by the present invention in minor amounts of usually not morethan 10%. Examples of such impact modifiers include chlorinatedpolyethylene, ABS polymers, and polyacrylate-butadiene graft copolymers.

The stabilizer composition of the invention, including the organotinmercapto acid ester and organotin sulfide, is employed in an amountsufficient to impart the desired resistance to heat deterioration atworking temperatures of 350° F. and above. The longer the time and themore rigorous the conditions to which the resin will be subjected duringworking and mixing, the greater will be the amount required. Generally,as little as 0.25% total of the stabilizer composition by weight of theresin, will improve resistance to heat deterioration.

There is no critical upper limit on the amount, but amounts above about15% by weight of the resin do not give an increase in stabilizingeffectiveness commensurate with the additional stabilizer employed.Preferably, the amount is from about 0.5 to about 5% by weight of theresin.

The proportion of the organotin mercapto acid ester and of the organotinsulfide is sufficient to give a sulfur content in the composition withinthe range from about 12 to about 25%, and a tin content within the rangefrom about 20 to 35%. For best results an overall sulfur content fromabout 22% to about 30% by weight of the stabilizer composition ispreferred. Accordingly, the proportions by weight of organotin mercaptoester to organotin sulfide will usually be within the range of 20:1 to1:2 and preferably within the range of 9:1 to 1:1.

The stabilizer combination of the invention is extremely effective whenused alone, but it can be employed together with other polyvinylchloride resin stabilizers, if special effects are desired. Thestabilizer combination of the invention in this event will be the majorstabilizer, and the additional stablizer will supplement the stabilizingaction of the former, the amount of the stabilizer combination beingwithin the range from about 0.25 to about 15 parts by weight per 100parts of the resin, and the additional stabilizer being in an amount offrom about 0.05 to about 10 parts per 100 parts of the resin.

Among the additional metallic stabilizers are included other organotincompounds, polyvalent metal salts of medium and of high molecular weightfatty acids and phenols, with metals such as calcium, tin, cadmium,barium, zinc, magnesium, and strontium. The non-metallic stabilizersinclude phosphites, epoxy compounds, and the like. Epoxy compounds areespecially useful, and typical compounds are described in U.S. Pat. No.2,997,454.

Generally, the stabilizer composition of this invention can be preparedby mixing the organotin mercapto acid ester with the organotin sulfide,either alone, or with any liquid lubricant or plasticizer to be added tothe resin composition with the stabilizer.

The preparation of the polyvinyl chloride resin composition is easilyaccomplished by conventional procedures. The selected stabilizercombination is formed as above, and then is blended with the polyvinylchloride resin, or alternatively, the components are blendedindividually in the resin, using, for instance, a two or three rollmill, at a temperature at which the mix is fluid and thorough blendingfacilitated, milling the resin composition including any plasticizer atfrom 250° to 375° F. For a time sufficient to form a homogeneous mass,five minutes, usually. After the mass is uniform, it is sheeted off inthe usual way.

For the commercial processing of rigid polyvinyl chloride, thestabilizer is conveniently mixed with all or a portion of the polymer tobe stabilized with vigorous agitation under such conditions of time andtemperature that the stabilizer is sufficiently imbibed by the polymerto produce a dry, free-flowing powder. The well-known Henschel mixer iswell suited to this procedure.

The following examples in the opinion of the inventor representpreferred embodiments of this invention:

.[.EXAMPLE 1.].

.[.A series of rigid or nonplasticized formulations was prepared havingthe following composition..].

    ______________________________________                                        .[.Ingredients:      Parts by weight                                          ______________________________________                                        Polyvinyl chloride homopoly-                                                  mer (Diamond 40)     100.                                                     Stabilizer           As shown in Table I.].                                   ______________________________________                                    

.[.The stabilizer concentrations used in each sample of resin testedcontained the amount of tin, shown in Table I below per 100 parts ofresin..].

.[.The stabilizer components were first mixed together in theproportions indicated in Table I below, and were then mixed in the resinon a two roll mill to form a homogeneous sheet, and sheeted off. Stripswere cut off from the sheet and heated in an oven at 375° F. for twohours to determine heat stability. Pieces of each strip were removed at15 minute intervals and affixed to cards to show the progressive heatdeterioration. The appearance of the samples is reported in Table Ibelow..].

    .[.TABLE I                                                                    __________________________________________________________________________    Examples                                                                      Control A         Amt.                                                                             Example 1   Amt. Example 2 Amt.                                                                             Control                                                                                Amt.               Stabilizer composition                                                       __________________________________________________________________________                         Monobutyltin tris(iso-                                                                       Monobutyltin tris(iso-                    Monobutyltin tris (iso-                                                                            octyl thioglycolate                                                                       1.90                                                                             octyl thioglyoclate                                                                       1.35                          octyl thioglycolate)                                                                            2.7                                                                              Dibutyltin sulfide                                                                        0.3                                                                              Dibutyltin sulfide                                                                        0.5                                                                              Dibutyltin                                                                             1.0fide           Tin (g.)          0.410                                                                            Tin (g.)    0.422                                                                            Tin (g.)    0.430                                                                            Tin (g.) 0.446             __________________________________________________________________________    Time (min.)                                                                         Color          Color          Color          Color                      __________________________________________________________________________    Initial                                                                             Colorless      Colorless      Colorless      Colorless.                 15    Slight yellow tint                                                                           Very slight yellow tint                                                                      Very slight yellow tint                                                                      Yellow.                    30    Very light yellow                                                                            Slight yellow tint                                                                           Slight yellow tint                                                                           "                          45    Light yellow   Very light yellow                                                                            Very light yellow                                                                            "                          60    Yellow         Light yellow   "              "                          75    Charred yellow yellow         Light yellow   Dark yellow                90    Black          Charred yellow Charred yellow Brown.                     105                  Black          Black.].                                  __________________________________________________________________________

.[.The results clearly indicate the improved effectiveness obtainable bycombinig dibutyltin sulfide, the highly concentrated organotin compound,with monobutyltin tris(isoctyl thioglycolate). The stabilizercombinations of this invention, 2.2 parts per 100 parts resin, asexemplified by Example 1, and 1.85 parts per 100 parts resin, asexemplified by Example 2, provided a very lightly colored, clearcomposition after 30 minutes of heating at 375° F. that was no morediscolored than Control A, containing monobutyltin tris(isooctylthioglycolate) in a higher total amount of stabilizer, i.e. 2.7 parts byweight per 100 parts resin, after 15 minutes of heating. The degree ofdiscoloration shown by Control A after 30 minutes was maintained by thesample of Example 1 for 45 minutes and by the sample of Example 2 for 60minutes of heating. Thus, the stabilizer compositions of this inventionconsiderably extend the processing period for resins before harmfuldiscoloration appears. Control B, containing dibutyltin sulfide alone,showed undesirable initial and early properties, i.e. the formation of ayellow discoloration in the resin within only 15 minutes after heatinghad begun..].

.[.EXAMPLES 3 THROUGH 5.].

.[.A series of rigid nonplasticized resin formulations was preparedhaving the following composition:

    ______________________________________                                        .[.Ingredients:      Parts by weight                                          ______________________________________                                        Polyvinyl chloride homopoly-                                                  mer (Diamond 40)     100.                                                     Stabilizer combination                                                                             As shown in Table II..].                                 ______________________________________                                    

.[.The same procedure was followed in preparing and testing thecompositions as in Example 1 and the appearance of the samples isreported in Table II below. Each resin sample contained the same totalamount of stabilizer, 2.2 parts by weight per hundred parts resin..].

    .[.TABLE II                                                                   __________________________________________________________________________    Examples                                                                      Control C    Amt.                                                                             Example 3                                                                              Amt.                                                                             Example 4                                                                              Amt.                                                                             Example 5                                                                              Amt.                                                                             Control                                                                              Amt.                Stabilizer composition                                                       __________________________________________________________________________    Monobutyltin    Monobutyltin tris                                                                         Monobutyltin tris                                                                         Monobutyltin tris                     tris (iso-      (isooctylthio-                                                                            (isoocytylthio-                                                                           (isooctylthio-                        octylthio-      glycolate)                                                                             1.76                                                                             glycolate)                                                                             1.605                                                                            glycolate)                                                                             1.425                                                                            Dibutyltin                glycolate)   2.2                                                                              Dibutyltin sulfide                                                                     0.44                                                                             Dibutyltin sulfide                                                                     0.595                                                                            Dibutyltin sulfide                                                                     0.775                                                                            sulfide                                                                              2.2                Tin (g.)     0.334                                                                            Tin (g.) 0.465                                                                            Tin (g.) 0.530                                                                            Tin (g.) 0.564                                                                            Tin                                                                                  0.980              __________________________________________________________________________    Time                                                                          (min.)                                                                              Color     Color       Color       Color       Color                     __________________________________________________________________________    Initial                                                                             Colorless Colorless   Colorless   Colorless   Colorless.                15    Very light yellow                                                                       Very slight yellow tint                                                                   Very slight yellow tint                                                                   Very slight yellow                                                                        Yellow                    30    Light yellow                                                                            "           "           "           "                         45    Yellow    Very light yellow                                                                         Very light yellow                                                                         Very light yellow                                                                         "                         60    Dark yellow                                                                             Light yellow                                                                              "           "           Dark yellow.              75    Black     Yellow      Light yellow                                                                              Light yellow                                                                              "                         90              Charred yellow                                                                            Yellow      Yellow      "                         105             Black       Charred yellow                                                                            Charred yellow                                                                            "                         120                         Black       Brown       Yellow-brown..].          __________________________________________________________________________

.[.The results clearly indicate that when used at equal totalconcentrations by weight, all of the claimed stabilizer combinations,monobutyltin tris(isooctyl thioglycolate) and dibutyltin sulfide,inhibit the deterioration of the resin upon heating at 375° F. for aperiod of time substantially longer than either component alone and thusincrease processing time before a harmful discoloration appears. ControlC acquires a very light yellow discoloration within 15 minutes ofheating but Examples 3, 4 and 5 maintain a less discolored appearancefor 45 minutes of heating. In addition, the resin compositions Examples3, 4 and 5 containing the novel combination of stabilizers maintain nomore than a light discoloration even after 90 minutes of heating at 375°F. Contrarily, Control C, the composition containing the monobutyltintris(isooctyl thioglycolate), acquires a dark discoloration after 60minutes and is black after 75 minutes of heating. Control D, although itdoes not turn black until after two hours of heating, discolorsimmediately, i.e. after 15 minutes of heating, to a yellow discolorationand maintains this undesirable color during the term of heating,acquiring a darker discoloration after 60 minutes..].

.[.EXAMPLES 6 THROUGH 8 .].

.[.Another series of rigid resin formulations was prepared having thefollowing composition:.].

    ______________________________________                                        .[.Ingredients:     Parts by weight                                           ______________________________________                                        Polyvinyl chloride homopoly-                                                  mer (Diamond 40)    100.                                                      Isooctyl epoxy stearate                                                                           3                                                         Stabilizer combination                                                                            As shown in Table                                                             III..].                                                   ______________________________________                                    

.[.The same procedure was followed in preparing and testing thecompositions as in Example 2 and the appearance of the samples arereported in Table III below. Each resin sample contained the same totalamount of stabilizer, 1.5 parts by weight per hundred parts resin..].

    .[.TABLE III                                                                  __________________________________________________________________________    Examples                                                                      Control E    Amt.                                                                             Example 6                                                                              Amt.                                                                             Example 7                                                                              Amt.                                                                             Example 8                                                                              Amt.                                                                             Control                                                                               Amt.               Stabilizer composition                                                       __________________________________________________________________________                    Monobutyltin                                                                              Monobutyltin                                                                              Monobutyltin                                          tris(isooctyl                                                                             tris(isooctyl                                                                             tris(isooctyl                         Monobutyltin    thioglycolate)                                                                         1.2                                                                              thioglycolate)                                                                         1.095                                                                            thioglycolate)                                                                         0.97                         tris(isooctyl   Dibutyltin  Dibutyltin  Dibutyltin  Dibutyltin                thioglycolate)                                                                             1.5                                                                              sulfide  0.3                                                                              sulfide  0.405                                                                            sulfide  0.53                                                                             sulfide 1.5               __________________________________________________________________________    Time                                                                          (minutes)                                                                          Color      Color       Color       Color       Color                     __________________________________________________________________________    Initial                                                                            Colorless  Colorless   Colorless   Colorless   Colorless.                15   Very light yellow                                                                        Very slight yellow tint                                                                   Very slight yellow tint                                                                   Very slight yellow                                                                        Yellow.                   30   Light yellow                                                                             Very light yellow                                                                         Very light yellow                                                                         Very light yellow                                                                         "                         45   Yellow     "           Light yellow                                                                              Light yellow                                                                              "                         60   Green      Light yellow                                                                              "           "           Dark yellow.              75   Black      Greenish yellow                                                                           Yellow      Yellow      "                         90              Black       Black       Green       "                         105                                     Black       "                         120                                                 Very dark                 __________________________________________________________________________                                                        yellow..].            

.[.The results of Table III clearly indicate the improved effectivenessobtained by combining dibutyltin sulfide, the highly concentratedorganotin compound, with monobutyltin tris(isooctyl thioglycolate) evenat the low total proportions by weight in the present example, i.e. 1.5parts per hundred parts resin. The samples containing the combination ofthe present invention, Examples 6, 7 and 8, inhibit the deterioration ofthe resin upon heating at 375° F. for a period of time substantiallylonger than either component alone. Control E turned a very light yellowwithin 15 minutes of heating, but Examples 6, 7 and 8 maintained a lessdiscolored appearance until 30 minutes of heating had elapsed..].

.[.In addition, the resin compositions of Examples 6, 7 and 8 containingthe novel combination of stabilizers maintained no more than a lightdiscoloration even after 60 minutes of heating. Contrarily, Control E,the composition containing the monobutyltin tris(isooctyl thioglycolate)alone acquired a dark discoloration after 30 minutes of heating andturned black after 75 minutes of heating. Control F, although it doesnot turn black until after two hours of heating, discolors immediately,i.e. after 15 minutes of heating to a yellow discoloration. It maintainsthis undesirable color during the term of heating and becomes a darkerdiscoloration after 75 minutes..].

EXAMPLES .Badd..[.9.]..Baddend. .Iadd.1 .Iaddend.THROUGH.Badd..[.11.]..Baddend. .Iadd.3 .Iaddend.

A series of rigid nonplasticized formulations was prepared having thefollowing composition:

    ______________________________________                                        Ingredients:     Parts by weight                                              ______________________________________                                        Polyvinyl chloride homopoly-                                                   mer (Diamond 40)                                                                              100.                                                         Stabilizer       As shown in Table .[.IV.]..Iadd.I..Iaddend.                  ______________________________________                                    

The stablizer combinations used in each sample of resin tested containedthe same total amount of tin, i.e. 0.55 part per 100 parts of resin. Thesame procedure was followed in preparing and testing the resins as inExample 1 and the appearance of the test samples are set out in Table.[.IV.]. .Iadd.I.Iaddend..

                                      TABLE .Iadd.I.Iaddend..[.IV.].              __________________________________________________________________________    Examples                                                                      Control .Iadd.A.Iaddend..[.G.].                                                             Amt.                                                                             Example .Iadd.1.Iaddend..[. 9.].                                                        Amt.                                                                             Example .Iadd.2.Iaddend..[.10.].                                                      Amt.                                                                             Example .Iadd.3.Iaddend..[.11.].                                              2       Amt.                                                                             Control                                                                       .Iadd.B.Iaddend..[.H.]                                                        .       Amt.               Stabilizer composition                                                       __________________________________________________________________________                     Dibutyltin bis-                                                                            Dibutyltin bis                                                                           Dibutlytin bis-                                       (isooctylthio-                                                                             (isooctylthio-                                                                           (isooctylthio-                       Dibutyltin bis-  glycolate)                                                                              2.52                                                                             glycolate)                                                                            2.07                                                                             glycolate)                                                                            1.48                         (isooctylthio-   Butyltin sesqui-                                                                           Butyltin sesqui-                                                                         Butyltin sesqui-                                                                         Butyltin sesqui-          glycolate)    2.96                                                                             sulfide   0.15                                                                             sulfide 0.30                                                                             sulfide 0.5                                                                              sulfide 1.0               __________________________________________________________________________    Time                                                                          (min.)                                                                            Color        Color        Color      Color      Color                     __________________________________________________________________________    Initial                                                                           Colorless    Colorless    Colorless  Colorless  Colorless.                15  Very light yellow                                                                          Very slight yellow tint                                                                    Very slight yellow tint                                                                  Very slight yellow                                                                       Light yellow.             30  "            "            "          "          Light tan.                45  Light yellow "            "          "          Tan.                      60  "            Very light yellow                                                                          Very light yellow                                                                        Very light yellow                                                                        Dark tan.                 75  "            "            "          "          Brown.                    90  Light yellow with brown                                                                    "            "          Light tan  Black.                        corners                                                                   105 Light yellow with brown                                                                    Light yellow with brown                                                                    Light yellow                                                                             "                                        edges.       corners.                                                     120 Yellow with brown                                                                          Light yellow with brown                                                                    Light yellow with                                                                        Tan                                      edges.       edges.       brown corners.                                  __________________________________________________________________________

The advantages of using the combinations of this invention in Examples.Badd..[.9, 10 and 11.]..Baddend. .Iadd.1,2 and 3 .Iaddend.are clearlyshown over the use of the components alone in Controls .[.G and H.]..Iadd.A and B .Iaddend.when used at equal parts of tin per 100 parts ofresin. As shown in Control .[.G,.]. .Iadd.A, .Iaddend.the dibutyltinbis(isooctyl thioglycolate), acquires a very light yellow discolorationwithin the first 15 minutes of heating. Examples .Badd..[.9 through11.]..Baddend. .Iadd.1 to 3 .Iaddend.maintain a lighter color for morethan 45 minutes and do not show the same discoloration until after 60minutes of heating have elapsed. This shows that the combination of thisinvention is four times as effective in stabilizing the resin at equalparts of tin. In addition, the total amount of stabilizer added issubstantially lower in Examples .Badd..[.9 through 11.]..Baddend..Iadd.1 to 3 .Iaddend.as compared to Control .[.G..]. .Iadd.A..Iaddend.Control .[.H.]. .Iadd.B .Iaddend.turns a light yellow colorwithin 15 minutes after heating and Examples .Badd..[.9 through11.]..Baddend. .Iadd.1 through 3 .Iaddend.do not become this discoloreduntil after 90 minutes of heating.

The stabilizer composition of this invention are advantageously used inresins formed into many useful structural members including extrudedpolyvinyl chloride pipe useful for water, brine, crude petroleum,gasoline, natural and manufactured fuel gas, and domestic and industrialwastes; flat and corrugated profiles for the construction industry, andblow-molded bottles. Typical formulations are as follows:

    ______________________________________                                        Pipe                                                                          Composition:             Parts by weight                                      ______________________________________                                        Medium mol. wt. polyvinyl chloride homopoly-                                   mer (K=55)              100                                                  ABS polymer              10                                                   Calcium stearate         1                                                    Dibutyltin sulfide       0.5                                                  .Iadd.Di.Iaddend.-n-butyltin bis(isooctyl thioglycolate)                                               0.9                                                  Pigment                  As desired                                           ______________________________________                                    

    ______________________________________                                        Parisons for blow-molding bottles                                             Composition:             Parts by weight                                      ______________________________________                                        Medium mol. wt. polyvinyl chloride homopoly-                                   mer(K=55)               100                                                  Styrene - butadiene - methyl methacrylate poly-                                mer                      10                                                  Stearic acid             0.5                                                  n-Butyltin sesquisulfide 0.5                                                  Di-n-butyltin bis(n-dodecyl thioglycolate)                                                             1.1                                                  Blue dye                 0.0005-0.002                                         ______________________________________                                    

    ______________________________________                                        Food-grade bottles                                                            Composition:             Parts by weight                                      ______________________________________                                        Medium mol. wt. polyvinyl chloride homopoly-                                   mer (K=55)              100                                                  ABS polymer              10                                                   n-Octyltin sequisulfide  0.5                                                  Di-n-octyltin bis(isooctyl thioglycolate)                                                              0.95                                                 Di-n-octyltin oxide      0.05                                                 ______________________________________                                    

    ______________________________________                                        Profiles                                                                      Composition:             Parts by weight                                      ______________________________________                                        High mol. wt. polyvinyl chloride homopoly-                                     mer(K=70)               100                                                  Chlorinated polyethylene (31% Cl)                                                                      15                                                   Isooctyl epoxystearate   2                                                    Di-n-octyltin sulfide    0.75                                                 .Iadd.Di.Iaddend.-n-butyltin .Iadd.bis.Iaddend..[.tris.].(isooctyl            thioglycolate)           1.0                                                  Magnesium stearate       0.25                                                 ______________________________________                                    

These formulations each contain sufficient stabilizer in accordance withthe invention to be processed at elevated temperatures into the desiredshapes without deleterious discoloration or embrittlement.

Having regard for the foregoing disclosure, the following is claimed asthe inventive and patentable embodiments thereof:
 1. A stabilizercomposition for improving the resistance to deterioration of polyvinylchloride resins when heated at 350° F., consisting essentially of anorganotin alpha- or beta-mercapto carboxylic acid ester having theformula ##STR29## wherein R' is an alkyl radical linked to tin throughcarbon and having from one to about eight carbon atoms, Z is a bivalentalkylene radical having from one to about two carbon atoms, and carryingthe --S-- and --COOR" groups, and R" is an organic group derived from amonohydric or polyhydric alcohol having from one to about two hydroxylgroups and from one to about fifteen carbon atoms, .Iadd.and .Iaddend.mis an integer from 1 to 2, .[.and n is an integer from 1 to 2,.]. theS--Z--(COOR")_(m) group being derived from an alpha- orbeta-mercaptocarboxylic acid ester; and an organotin sulfide having theformula R₂ SnS, in which R is alkyl linked to tin through carbon and hasfrom one to about eight carbon atoms, the organotin compounds togethercomprising an amount of tin within the range from about 20 to about 35%by weight, and an amount of sulfur within the range from about 10 toabout 35% by weight.
 2. A stabilizer composition in accordance withclaim 1, in which the organotin mercaptocarboxylic acid ester is anorganotin thioglycolate.
 3. A stablizer composition in accordance withclaim 1, in which the organotin sulfide is dibutyl tin sulfide and theorganotin mercaptocarboxylic acid ester is .[.monobutyl.]. .Iadd.dibutyl.Iaddend.tin or .[.monooctyl.]. .Iadd.dioctyl .Iaddend.tin.[.tris(isooctyl.]. .Iadd.bis(octyl .Iaddend.tin thioglycolate. .[.4. Astabilizer composition according to claim 1, in which n is 1..].
 5. Astabilizer composition according to claim .[.4,.]. .Iadd.1, .Iaddend.inwhich the organotin mercaptocarboxylic acid ester is .[.monobutyl.]..Iadd.dibutyl .Iaddend.tin .[.tris(isoocytyl.]. .Iadd.bis(isooctyl.Iaddend.thioglycolate) and the organotin sulfide is dibutyl tinsulfide. . A stabilizer composition according to claim .[.4.]. .Iadd.1.Iaddend.in which the organotin mercaptocarboxylic acid ester is.[.monobutyl.]. .Iadd.dibutyl .Iaddend.tin .[.tris(isoocotyl.]..Iadd.bis(isoocotyl .Iaddend.thioglycolate) and the organotin sulfide isdioctyl tin sulfide. . A stabilizer composition according to claim.[.4,.]. .Iadd.1 .Iaddend.in which the organotin mercaptocarboxylic acidester is .[.monobutyl.]. .Iadd.dibutyl .Iaddend.tin .[.tris(isooctyl.]..Iadd.bis(isooctyl .Iaddend.thioglycolate).
 8. A stabilizer compositionaccording to claim .[.4,.]. .Iadd.1 .Iaddend.in which the organotinsulfide is dibutyl tin sulfide.
 9. A polyvinyl chloride resincomposition having an enhanced resistance to deterioration when heatedat 350° F., consisting essentially of a polyvinyl chloride resin and astabilizer composition in accordance with claim
 1. 10. A polyvinylchloride resin composition in accordance with claim 9 in which thepolyvinyl chloride resin is polyvinyl chloride homopolymer.
 11. Apolyvinyl chloride resin composition in accordance with claim 9 in whichthe polyvinyl chloride resin is a copolymer of vinyl chloride and vinylacetate.
 12. A polyvinyl chloride resin composition in accordance withclaim 9 in which the amount of stabilizer composition is within therange from about 0.25% to about 15% by weight of the composition.
 13. Apolyvinyl chloride resin composition in accordance with claim 9including in addition a polyvalent metal salt of an aliphatic fattyacid.
 14. A polyvinyl chloride resin composition in accordance withclaim 9 including in addition an organic phosphite.
 15. A polyvinylchloride resin composition in accordance with claim 9 including inaddition an epoxy compound.
 16. A polyvinyl chloride resin compositionin accordance with claim 9 including in addition a plasticizer for theresin in an amount in excess of about 15% by weight. . A rigid polyvinylchloride resin composition in accordance with claim 9 comprising aplasticizer in an amount up to about 10% by weight of the composition.